Food patty molding machine

ABSTRACT

A food patty molding machine of the type utilizing a linearly reciprocable mold plate utilizes a direct rotary actuator drive which provides virtually direct linear transfer of the drive force to the ends of the linear drive shafts which support the mold plate. This results in the virtual elimination of high wear lateral loads. An encoder is directly linked to the rotary actuator drive shaft to provide accurate mold plate position signals which are utilized to control the operation of completely independently driven knock-out devices and to control operation of the feed ram during the feed stroke. Servo valve control of the hydraulic power unit which drives the rotary actuator and the feed ram cylinders also responds to suitably processed encoder signals to provide a wide range of speed and position control.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 08/799,116, filed Feb.11, 1997, now U.S. Pat. No. 5,730,650, which is a continuation-in-partof application Ser. No. 08/706,405, filed Aug. 9, 1996, now U.S. Pat.No. 5,655,436.

BACKGROUND OF THE INVENTION

The present invention pertains to a food patty molding machine and, moreparticularly, to an improved drive assembly and control system for sucha machine.

Machines for the high volume production of molded food patties are wellknown in the art. Such machines are used typically to form hamburgerpatties from a supply of ground beef by forcing the ground beef underpressure into a multi-cavity mold plate which is rapidly shuttled on alinear slide between a fill position and a discharge position in whichvertically reciprocable knock-outs push the patties from the moldcavities. U.S. Pat. No. 3,887,964 discloses the basic construction of afood patty molding machine which is basically unchanged and remains incurrent use. The machine disclosed in that patent utilizes a variablespeed motor-driven reducer which operates a rotary crank mechanism andcooperating mechanical linkage which converts the rotary motion to.reciprocable motion to drive the mold plate between its fill anddischarge positions. The mechanical linkage includes a hydraulicallybuffered lost motion mechanism which is utilized to provide a shortdwell in each of the mold plate fill and discharge positions. Thevariable speed drive is also mechanically linked to the knock-outs fordischarging the patties from the mold plate in a manner which timesoperation of the knock-outs directly and mechanically to thereciprocable operation of the mold plate.

A number of disadvantages have been found to be attendant to theconstruction and operation of the above described food patty moldingmachine. The mechanical drive linkage includes a significant number ofindividual components resulting in a rather complex mechanism. An offsetconnection of the lost motion drive mechanism to the ends of the moldplate carriage results inherently in the imposition of significantlaterally directed loads on the carriage slide mechanism. These lateralloads, in turn, have been found to cause substantial rapid wear to thelinear drive shafts and supporting linear bearings which comprise thereciprocating carriage. Excessive wear can eventually lead tomisalignment beyond the range of attainable adjustment, fracture of moldplates, and other potential damage if not closely monitored. At best,rapid wear of the mold plate carriage linear drives and bearings createsa chronic maintenance and replacement part problem. Also, the lostmotion drive which is utilized to provide short dwell periods at theends of the fill and discharge positions, is not easily adjustable tocompensate, for example, for changes in temperature of the supply ofground meat or ground food product. Furthermore, because operation ofthe mold plate and the knock-outs is linked mechanically, there is nopossibility of halting operation of one or the other of the subsystemsin the event of a problem, such as misalignment of the mold plate withthe knock-out cups in the discharge position. In addition, because ofthe. strict requirements imposed on machinery used in the processing offood for human consumption, the applicable regulations require rigorouscleaning procedures, in particular high pressure washing with water.Prior art machines have not been very tolerant to high pressure washingand, as a result, periodic washing often results in shorted electricmotors and other electric components, rust and corrosion, loss oflubricant from grease fittings, all adding considerably to the time andcost of maintenance and repair.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a patty moldingmachine of the type utilizing a linearly reciprocable mold plate isprovided with a direct rotary actuator drive which provides virtuallydirect linear transfer of the drive force to the ends of the lineardrive shafts supporting the mold plate and the virtual elimination ofhigh wear lateral loads. The rotary actuator is operable to providevariable speed operation and closely controllable positioning in amanner obviating the need for complex lost motion linkages. An encoderdirectly linked to the output of the rotary actuator is used to controlthe operation of a completely independently driven knock-out mechanism,obviating the need for a timed mechanical link between the mold plateand the knock-outs.

The improved drive apparatus, according to one aspect of the presentinvention, includes a main drive arm having a drive end fixed forreciprocable rotational movement on an axis which is parallel to andspaced from the plane of the mold plate linear drive shafts and a drivenend which is positioned to move in a shallow arc substantially in thatsame plane. A rigid linear drive link has a first link end rotatablyconnected to the end of one of the linear drive shafts for movementtherewith in said plane, and a second link end rotatably connected tothe driven end of the drive arm for movement therewith in the shallowarc. A direct drive provides reciprocable rotation to the drive arm.

Preferably, a main drive arm is provided for each linear drive shaft. Amain driving shaft provides a fixed connection for the drive end of eachof the main drive arms and defines the axis of rotation for said drivearms. A driving connection is provided between said direct drive and themain driving shaft. The direct drive preferably comprises a rotaryactuator and the main driving shaft comprises the output shaft of saidrotary actuator. In the preferred embodiment, the rotary actuator ishydraulically driven.

The drive apparatus of the present invention provides positions betweena top dead center position of the drive arms and each of the fillposition and the discharge position of the mold plate in which each ofthe linear drive links is positioned colinearly with its respectivelinear drive shaft. In both of the fill and discharge positions and inthe top dead center position, the linear drive links are positionedsubstantially equiangularly with respect to their respective lineardrive shafts. To minimize undesirable lateral loading, the extremeequiangular positions of the drive links with respect to the driveshafts are preferably no greater than about 7.5°, and the total arc ofrotation between each drive link and its respective drive arm ispreferably no greater than about 15°.

In an alternate embodiment, the direct drive may comprise a linearhydraulic cylinder. The main shaft is preferably provided with a crankarm to which the hydraulic cylinder is attached to provide the directdriving connection Other drive means, such as an electric servomotorcould also be utilized to provide a direct driving connection to themain driveshaft. Although the use of a rotary hydraulic actuator and apair of drive arms provides a compact drive arrangement, alternatedriving arrangements which completely eliminate the drive arms couldalso be utilized. For example, linear racks disposed parallel to andconnected to the ends of the reciprocating linear driveshafts could bedirectly driven by servomotor operated pinions in direct engagement withthe racks. It is believed, however, that such an alternate arrangementwould not as efficiently utilize the available space below the plane ofthe mold plate, as does the presently preferred embodiment.

In accordance with another aspect of the invention, a meat productmolding machine of the type described includes a horizontally operablefeed ram which is disposed to move reciprocally in a meat feed chamberreceiving ground meat from an upper supply hopper, the ram being movablethrough a forward stroke to transfer meat from the feed chamber througha distribution manifold and into the mold cavity of a mold platepositioned in a fill position, which mold plate is movable in a linearreciprocable path between the fill position and a discharge position,the machine further including a vertically reciprocable knock-out deviceoperable to pass through the mold plate in the discharge position topush the product from the mold cavity, and a pair of parallel laterallyspaced linear drive shafts supporting the mold plate for movementtherewith along the linear mold plate path, the improvement whichcomprises a pair of drive arms, each having a drive end attached to amain driving shaft for reciprocable rotational movement therewith abouta driving shaft axis disposed parallel to and spaced from the plane ofthe linear drive shafts, each drive arm having a driven end connected tothe end of a linear drive shaft to deliver a direct substantially lineardriving force along the drive shaft axis; an encoder responsive to thereciprocable rotational movement of the main driving shaft to providecontrol signals which are representative of mold plate position at andbetween the fill and discharge positions; and, means responsive to theencoder control signals to independently drive the ram and the knock-outdevice.

In accordance with yet another aspect of the invention, controlledoperation of the food product molding machine of the present inventionis provided by a method including the steps of driving the lineardriveshafts to continuously cycle the mold plate in its reciprocal path,monitoring the mold plate position over the full cycle of mold platemovement, generating control signals which are representative of moldplate position, commencing forward movement of the feed ram to feed amultiple food product into the mold plate cavity in response to afill-on control signal generated during the return stroke, terminatingforward movement of the ram and the feeding of food product to the moldcavity in response to a fill-off control signal which is generatedduring the discharge stroke, holding the mold plate for a dischargedwell time in the discharge position in response to a discharge positionsignal, and selectively adjusting the discharge dwell time to vary themold plate cycle time.

The method may also include the step of holding the mold plate for adwell time in the fill position in response to a fill position signal.In the preferred embodiment of the machine, a pair of alternatelyoperable feed rams are utilized. Each ram is adapted to move through oneforward stroke during multiple mold plate cycles and to return in areverse stroke in response to an end of stroke signal. The end of strokesignal operates to cause initial movement of the other ram through itsforward stroke, and the method may also include the step of utilizingthe fill-on and fill-off control signals to provide a mold fill periodof delay of the response to the end of stroke signal.

In a variant method for operating a food patty molding machine of thetype having a mold plate with the mold cavity, which plate is cycled ina linear reciprocable path that is defined by a return stroke to a fillposition, an opposite discharge stroke to a discharge position, and adischarge dwell time in the discharge position, the method comprisingthe steps of: providing a drive for continuously cycling the mold platein its reciprocal path, monitoring the mold plate position over the fullcycle of mold plate movement, generating control signals which arerepresentative to mold plate position, feeding a moldable food productto the mold plate cavity in response to a fill-on control signal whichis generated during the return stroke, terminating the feed step inresponse to a fill-off control signal which is generated during thedischarge stroke, and varying the time of the complete mold plate cycleby adjusting the discharge dwell time.

A related drive system for operating the food product molding machineincludes means for driving the linear drive shafts to continuously cyclethe mold plate, means for monitoring the mold plate position over thefull cycle of movement and for generating control signals representativeof mold plate position, means for commencing forward movement of one oftwo feed rams to feed multiple food product to the mold plate cavity,means for terminating forward movement of said one ram and the feed offood product to the mold cavity, and means for holding the mold plate inthe discharge position for a selectively variable discharge dwell time.The means for commencing forward movement of the ram is preferablyresponsive to a fill-on control signal generated during the returnstroke. The means for terminating forward movement of the ram ispreferably responsive to a fill-off control signal generating during thedischarge stroke. The means for holding the mold plate for a dwell timeis preferably responsive to a discharge position signal.

The system preferably includes means for holding the mold plate in thefill position for a selectively variable fill dwell time. The fillposition holding means is preferably responsive to a fill positionsignal. The system preferably also includes means responsive to an endof ram feed stroke signal for reversing the operative ram and forcommencing the feed stroke of the other ram, and delay means for holdingthe response to the end of feed stroke signal until generation of thenext fill-off signal. The means for adjusting the discharge dwell timeis also preferably responsive to a change in fill dwell time to maintaina constant mold plate cycle time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of the food patty molding machine of thepresent invention.

FIG. 2 is a plan view, partly in section, of the apparatus shown in FIG.1 and taken on line 2--2 thereof.

FIG. 3 is a horizontal section taken on line 3--3 of FIG. 1.

FIG. 4 is a vertical section taken on line 4--4 of FIG. 1.

FIGS. 5 and 6 are enlarged sectional details taken on lines 5--5 and6--6, respectively, of FIG. 3.

FIG. 7 is a vertical side sectional view of the mold plate and knock-outportions of the machine in the mold fill position.

FIG. 8 is a vertical side sectional view similar to FIG. 7 showing themold plate in the discharge position.

FIG. 9 is a view similar to FIG. 8 showing operation of the dischargeknock-out device.

FIG. 10 is a sectional detail of the rotary actuator shown in FIGS. 1and 4 showing the stroke adjustment feature.

FIG. 11 is a sectional detail taken on line 11--11 of FIG. 2.

DETAILED DESCRIPTION

Referring initially to FIGS. 1-4, a patty molding machine 10 of thepresent invention is mounted substantially atop a generally rectangularframe 11, except for the main drive 12 for the patty mold plate, whichmain drive is mounted to depend downwardly from the upper main framemembers 13. The remainder of the interior of the frame provides ahousing for the hydraulic power unit, controls and circuitry therefor,and the electrical and microprocessor controls (none of which areshown).

Ground beef or other ground food product is loaded into a supply hopper14 where it is moved forwardly by an underlying supply conveyor 15 intoa vertically disposed feed hopper 16 at the downstream end of the supplyconveyor. Beneath the supply conveyor and extending directly below thebottom of the feed hopper 16 are a pair of laterally disposedhorizontally reciprocable feed rams 17. The rams are rectangular incross section and operate side-by-side in a pair of rectangular shapedfeed chambers 18 which lie substantially below the feed hopper 16. Thefeed chambers are defined by laterally opposite side walls 20, a commonbottom plate 21, a common center wall 22, and a common top plate 23which extends forwardly from a rear edge 24 adjacent the forward edge ofthe feed hopper 16. Thus, the feed hopper has an open bottom allowingthe food product to be fed vertically downwardly into a feed chamber 18when the ram 17 is withdrawn from the chamber, but which opening isclosed as the ram is stroked forwardly through the chamber beneath thefeed hopper 16 and then beneath the top plate.

A product distribution manifold 25 is mounted to extend across themachine, beneath the top plate 23 and abutting the downstream end 26 ofthe bottom plate 21. Thus, the manifold defines the downstream end ofthe feed chambers 18 and provides an opening for the ground meat orother food product as it is transferred under pressure of one of therams 17 from the feed chamber to the mold cavities in an upper moldplate 27. A rotary manifold valve 28 operates in the interior of themanifold 25 to direct food product delivered by the ram 17 which isoperating in its feed stroke to the mold plate, and to close off thefeed chamber 18 for the other ram in the retracted position to allow thefeed chamber to be filled from the feed hopper 16. Thus, the feed rams17 operate alternately, as shown in the drawings, but are fed by thecommon feed hopper 16. The hopper includes three vertically driven feedaugers 30 which, in a manner known in the prior art, are driven byseparate motors 29 and operated in pairs to deliver food product to thefeed chambers. The center feed auger 30 and the adjacent auger areoperated to fill the chamber from which the ram is withdrawn, while theopposite auger, above the ram moving in its feed stroke, is inoperative.Each of the rams 17 is independently driven by a hydraulically drivenram cylinder 31 mounted on the upper frame members 13 below the supplyhopper 14.

The top plate 23 which defines the top wall of the downstream ends offeed chambers 18, also overlies the manifold 25 and supports the moldplate 27 which slides reciprocally over the top plate between a fillposition above the manifold 25 (see FIG. 7) and a discharge position inwhich most of the mold plate is extended substantially beyond the topplate 23 and manifold 25 (see FIGS. 8 and 9). The top of the mold plate27 in the fill position is covered by a breather plate 32, allowing airto escape during mold plate filling, and the entire mold station isoverlain by the housing for a knock-out device 30 which is supported ona cover plate 34. The cover plate and the entire knock-out device 33supported thereon are mounted on a lift system (not shown) by which thecover plate may be raised to permit access to the molding station, asfor mold plate change, maintenance and cleaning, or the like.

The mold plate 27 is of a conventional construction and comprises a thinrectangular plate with a series of laterally aligned circular openingsdefining mold cavities 35 in which the ground meat or other food productpatties are formed. The mold plate is attached to and carried betweenits fill and discharge positions on a pair of laterally spaced lineardrive shafts 36. The drive shafts are of circular cross section and eachlinear drive shaft is mounted for sliding reciprocal motion in a shuttlebar 37 mounted to the side edge of the top plate 23. The linear driveshafts 36 are connected by a laterally disposed draw bar 28. Thedownstream edge of the mold plate 27 is bolted or otherwise demountablyattached to the draw bar 38 to support the mold plate for reciprocalmotion with the drive shafts 36. An upstream portion of the mold plateis always retained between the top plate 23 and the breather plate 32 asit shuttles between the fill and discharge positions.

It should be noted that a single feed stroke of a feed ram 17 willprovide enough product for many mold plate cycles. Thus, referring toFIG. 2, the upper ram 17 is shown near the end of its feed stroke,during which the mold plate cavities 35 (of which there are five in thisexample) will have been filled, shuttled to the downstream dischargeposition where the knock-out device 33 moves vertically to push thepatties from the mold cavities, and recycled through the fill-dischargecycle as many as 15 to 20 times during one feed stroke of the ram.

In the presently preferred embodiment, the linear drive shafts 36 whichcarry the reciprocal mold plate 27 are driven by a rotary actuator 40 ina manner which provides virtually direct linear transfer of the rotarydriving force from the actuator to the ends of the linear drive shafts,resulting in the virtual elimination of high wear lateral loads typicalof prior art devices. The rotary actuator 40 is attached to theunderside of the upper main frame members 13 with a mounting bracket 41.The rotary actuator shown is of the two cylinder type in which upper andlower actuator cylinders 42 and 43 are mounted and operated to strokesimultaneously in opposite directions to provide reciprocal rotarymovement to a main driving shaft 44 mounted to extend laterally throughthe actuator between the cylinders 42 and 43. In a manner well known inthe art, the operating pistons of the actuator cylinders are toothedracks 45 and the driving shaft 44 includes a pinion (not shown) mountedon the center of the shaft 44 and captured between the opposed toothedracks 45. The actuator may be supplied by a suitable controlled supplyof hydraulic pressure to alternately stroke the actuator cylinders 42and 43 in opposite directions to provide the desired reciprocatingrotary motion to the main driving shaft 44. Each end of the drivingshaft 44 is connected with a suitable coupling 46 to an axially alignedstub shaft 47 rotatably supported in a bearing 48. Each of the bearings48 is, in turn, mounted on a bearing support plate 50 attached to theupper main frame 13.

A main mold plate drive arm 51 is clamped by a drive end 49 to the outerend of each stub shaft 47 for reciprocal rotation therewith. The drivearms 51 extend upwardly to driven ends 52, each of which is connected tothe end of one of the linear drive shafts 36. The driven ends 52 of thedrive arms necessarily operate in a circular arc, but the significantlength of the drive arms and the relatively small rotational arc throughwith the arms rotate result in the driven ends 52 traveling through ashort shallow arc which does not depart significantly from thehorizontal plane of the linear drive shafts 36. In other words, thedriven end of the drive arm, through the full range of its reciprocalrotation, remains substantially on the axis of the linear drive shaft 36to which it is attached. However, this small amount of rotationalmovement requires each connection to be made with a short drive link 53.Each drive link has a flat end 54 which is pinned in a clevis formed inthe driven end 52 of the drive arm and a clevis end 55 which isconnected to the free end of the linear drive shaft 36, such as with arod end bearing 56.

Full stroke of the mold plate from its fill position to its dischargeposition requires only 300 of rotation by the rotary actuator 40 andthus 300 rotation of the drive arms 51. In the extreme positions of filland discharge, the drive links 53 are only angled about 7.50 downwardlyfrom the horizontal and thus rotate with respect to their pinnedconnections to the driven ends 52 of the drive arms through a total arcof only about 15°. The actuator is positioned midway between theextremes of drive arm rotation and the drive arms are positioned tosweep a shallow arc which carries the upper driven ends above thehorizontal plane of the axes of the linear shafts 36. Thus, at the topdead center position of the drive arms, the driven ends of the arms (andthe ends 54 of the drive links connected thereto) are above the plane ofthe linear shafts. In this position, the drive links are angled upwardlyfrom the horizontal by about the same 7.50. In the two mid-positionsbetween drive arm top dead center and the fill and discharge positions,the drive links are horizontal and each driven end 52 of a drive armlies directly on the axis of the linear shaft 36 to which it isconnected. As a result, the mold plate driving force is always imposednearly linearly on the linear drive shafts, resulting in a very minor,if any, lateral force component tending to lift up or pull down on thedrive shaft ends, depending on the direction of motion and drive armposition. This arrangement causes far less wear on bearing surfaces 57in the shuttle bars 37 through which the linear drive shaftsreciprocate. Also very important is the minimization of transfer ofvertical loads imposed on the ends of the linear drive shafts downstreamto the points where the draw bar 38 and mold plate 27 are connected. Asmay be seen in the mold plate in FIG. 2, the relatively large moldcavities 35 result in fairly small web sections in the mold platebetween the cavities. Vertical up and down loads imposed on the lineardrive shaft ends because of the non-linear drive linkages typical ofprior art machines often result in fracture of the mold plate.

The manifold valve 28 is basically a ported cylindrical sleeve whichoperates with a reciprocal rotational movement inside the manifold 25.The manifold valve 28 is operated with a small rotary actuator 58mounted on one of the upper side frame members 13 and having a directaxial driving connection to the valve 28. The actuator 58 may beidentical to rotary actuator 40, except that it is of a much smallersize. Operation of the small rotary actuator 58 and thus the manifoldvalve 28 are driven in timed relation to the cyclic reciprocation of thefeed rams 17. Referring particularly to FIGS. 4-6, the manifold valve 28is positioned to uncover and open a pair of feed slots 60 at the end ofthe feed chamber 18 carrying the ram which is being stroked in the feeddirection. That orientation of the manifold valve 28 automaticallycloses the feed slots 60 in the feed chamber for the other ram 17 whichhas been withdrawn or is being withdrawn to refill its feed chamber. Themanifold valve 28 is provided with two pairs of feed passages 61 of asize and shape to correspond to the feed slots 60, but with the pair offeed passages for one of the feed chambers displaced circumferentiallyaround the cylindrical manifold valve so the valve covers and closes thefeed slots in the chamber from which product is not being fed. Thecircumferentially opposite side of the manifold valve has a full lengthtransfer passage 62 which extends circumferentially around the valve farenough so that it remains open to permit passage of the food productupwardly and out of the manifold regardless of which feed passages 61are being utilized. From the transfer passage 62, the product passesthrough an upper outlet passage 63 in the manifold 25 and verticallyupward through a fill slot 64 in the top plate 23 which overlies themanifold. Actually, the fill slot is formed in an insert plate 65 placedin a suitable opening in the top plate 23. This permits exchange of fillslots to accommodate different products, different mold plates, and thelike. As may be seen best in FIGS. 5 and 6, ground meat or other foodproduct passing through the fill slot 64 moves directly into the moldcavities 35 which overlie the fill slot when the mold plate is in theretracted fill position. The filled mold plate is slid forward to thedischarge position (FIGS. 8 and 9) where a ganged array of knock-outcups 66 is moved downwardly simultaneously to push the molded foodpatties downwardly out of the mold cavities. The knock-out device 33includes a short stroke knock-out cylinder 67 mounted within the upperhousing 68 and operable to move one end of a lever arm assembly 70, theopposite end of which carries ganged knock-out cups 66. The knock-outdevice is driven completely independently of the mold plate drive, withits operation timed with respect to the mold plate drive by signalsgenerated from the drive in a manner which will be described.

With the feed ram 17 moving forwardly in its feed stroke (such as theram 17 shown uppermost in FIGS. 2 and 3), the manifold valve 28 ispositioned as shown in FIG. 6 to allow the meat product to pass throughthe manifold feed slots 60 in the manifold, the aligned feed passages 61in the valve, through the interior thereof, and upwardly through thetransfer passage 62, outlet passage 63 and fill slot 64, and into themold cavities 35, all as previously described. While the mold plate isin the fill position, it may be held there for a short dwell period toaccommodate filling. Utilizing a rotary actuator 40 for the main moldplate drive, the dwell may be provided by simply halting rotary motionof the actuator for the desired dwell period. This eliminates the needto utilize complex hydromechanical lost motion devices typical of theprior art. When the rotary actuator is again operated to move the moldplate to the discharge position, another short dwell period is providedwhile the knock-out cylinder 67 is actuated to operate the knock-outs 66which pass vertically downwardly through the mold cavities 35 in themold plate, as shown in FIG. 9.

There may be only 0.1 inch (2.5 mm) total clearance between theknock-out cups 66 and the side walls of the mold cavities 35. Therefore,it will be understood that extremely accurate positioning of the moldplate in the discharge position is required. Precise positioning of themold plate in the discharge position is easily accommodated with controlsignals generated by an encoder 73 mounted to be driven by the rotaryactuator drive, as will be described hereinafter.

In the operation of prior art devices, when the mold plate is moving tothe discharge position and the fill slot 64 in the top plate is coveredand closed by the solid portion of the mold plate, there will be apressure build up in the ram cylinder 31 which continues to advance inits feed stroke. In the prior art, a pressure responsive device on thecylinder senses the increase in pressure and halts the advance of theram until the mold plate has returned or is returning to the fillposition at which time the ram may be actuated by a sensed pressuredecrease to continue to advance in the feed stroke. As is also typicalof prior art devices, operation of the knock-out device is timed by adirect mechanical link to the main mold plate drive. With thismechanical link, inaccurate positioning of the mold plate in thedischarge position, resulting for example from wear in the drivelinkage, may result in catastrophic contact between the knock-outs andthe mold plate.

In accordance with the present invention, overpressure sensing controlof the feed strokes of ram cylinders 31 and mechanically linked timedoperation of the knock-outs are both eliminated. An encoder 73 isdirectly connected to the main driving shaft 44 to operate directly inresponse to reciprocal rotation thereof to generate control signalswhich are very accurately representative of the mold plate position atand between the fill and discharge positions. These signals may then beutilized to provide accurate timed operation of the feed stroke movementof the rams and the operation of the knock-out device. For example, toenhance cycle speed and efficiency, an encoder signal may be utilized onthe return stroke of the mold plate from the discharge to the fillposition to generate a fill-on signal as the mold cavities approach thefill slot to reactivate the ram to advance. The ram continues to advancewhile the mold plate returns to the fill position, is held there for ashort dwell period and begins reverse movement toward the dischargeposition. When the mold plate reaches a selected fill-off position, anencoder signal is processed to deactivate the ram once again. Similarly,encoder signals may be utilized to activate knock-outs only when themold plate is in the discharge position.

Position sensors on the knock-out device 33 are also utilized to preventoperation of the mold plate in the event the knock-outs are misalignedor not operating properly. The knock-out cylinder 67 is operable inresponse to an encoder signal to stroke the knock-outs only when themold plate is in the discharge position. Appropriate proximity sensorsdetect the down position of the knock-outs, assuring they have strokedproperly, and allows them to retract. The up position of the ejectors isindependently detected to confirm they have been properly retractedbefore the mold plate can be stroked back to the fill position. Thisseparate independent operation of the mold plate and knock-out deviceavoids the potential problems of prior art devices which aremechanically linked and forced to cycle together, even in situations ofpotentially catastrophic misalignment.

Referring again to FIG. 1, there is shown a basic schematic of use ofthe encoder signals to operate the system power unit to provide acontrolled supply of hydraulic fluid for various operating subsystems ofthe machine. The power unit 74 includes the usual motor-driven hydraulicpump, associated control valves, fluid supply and return lines, andreservoir, all as is well known in the art. Direct control of the powerunit is accomplished via a hydraulic servo valve 75 which receivessignals from the encoder 73 with the signals suitably processed by anintermediate microprocessor 76. For example, encoder signalsrepresentative of the fill and discharge positions of the mold plateprovide the basis for precisely determining the mold plate positionanywhere in between and during plate movement in either direction. Theseencoder signals can then be processed by the microprocessor 76 to, forexample, actuate the ram cylinder 31 at any selected position of themold plate in the return stroke, set the dwell time of the mold plate inthe fill position, shutoff the cylinder and associated feed ram 17 atany selected position in the mold plate discharge stroke, and provide adischarge position signal allowing the knock-out device 33 to beactuated. Cycle speed may also be changed by variable control of theservo valve 75 in either direction of mold plate movement. In thismanner, total cycle time can be adjusted without changing or otherwiseaffecting the fill portion of the cycle. The portion of the mold platereturn stroke between knock-out and the fill-on position where the ramis again activated provides one zone of speed adjustment. The otherspeed adjustment zone comprises the portion of the discharge strokebetween the fill-off position and the end of the discharge stroke at theknock-out position.

The rotary actuator 40 is preferably operated to provide uniformacceleration and deceleration in both the return stroke and thedischarge stroke, and to operate both strokes at the same speed. Cycletime may be conveniently and simply varied by adjusting the dwell timein the discharge position. In this manner, the fill portion of the cycleis totally unaffected which is extremely important in maintaining theuniformity of the molded food product. In the practical operation of amolded food processing plant, factors both upstream and downstream ofthe patty molding machine of the present invention may require or makeit desirable to operate the machine at a slower or faster speed. Forexample, if the supply of meat to the hopper 14 is interrupted orslowed, the machine cycle time may need to be correspondingly slowed toavoid exhaustion of the food supply. Similarly, downstream interruptionsin equipment or processes for handling the formed food patties may makeit necessary or desirable to temporarily slow the cycle time of themachine. In prior art machines, slowing the cycle time caused a uniformslowing of the entire cycle, including the fill portions of the returnand discharge strokes. However, corresponding adjustment of the fill-onand fill-off positions could not be effected and, as a result, theconsistency and/or quality of the molded food products varied.

It may also be necessary or desirable to adjust the fill portion of thecycle and to do so without changing the cycle time. For example, asignificant change in the temperature of the food product being suppliedto the machine will have a significant affect on how the product molds.If the temperature of the food product supply drops significantly, itmay be necessary to adjust the timing of the fill-on or fill-off signalsor to increase the fill position dwell time. A change in the latterwould normally cause a change in cycle time. However, with the presentmachine, any change in the fill position dwell time can be compensatedwith an identical, but opposite change in the discharge dwell time and,as a result, the cycle time remains unchanged.

With the use of a programmable controller in the microprocessor 76, itis possible to establish parameters for optimum molding of a particularfood product based on its known content, supply temperature, and otherfactors, and to program the optimum fill-on, fill dwell, and fill-offtimes in the microprocessor controller. The machine may then be operatedat any desired speed by appropriate adjustment of the discharge dwelltime (within the range of available cycle times) without altering thecritical mold fill portion of the cycle.

As indicated previously, the feed chambers 18 and length of stroke ofeach of the rams 17 is designed to provide multiple mold plate fillcycles per ram feed stroke. In the prior art the end of the ram feedstroke is sensed by an appropriate limit switch or proximity sensor andthe signal generated is used to begin feed stroke movement of the otherram 17 and to halt and reverse the ram which has reached the end of itsfeed stroke. However, if the mold plate is being filled when feed isshifted from one ram to another, an intermittent halt in product flowmay result in the mold cavities 35 being only partially filled and, ofcourse, defective molded food products. However, in the present machine,the encoder keeps accurate track of the exact position of the mold plateand, if the encoder signals indicate that the mold plate is anywherebetween the fill-on and fill-off positions, the manifold valve 28 willnot be rotated and the other ram will not begin its feed stroke untilthe fill portion of the cycle has been completed, in other words, untila fill-off signal from the encoder has been processed.

Prevention of inadvertent over-travel by the rotary actuator 40 iseasily and accurately accomplished by utilizing the actuator strokeadjuster 71 shown in FIG. 10. The stroke adjuster comprises a largethreaded stud 72 which may be adjusted axially within one of theactuator cylinders 42 or 43 to provide a physical end stop for travel ofthe toothed rack 45 in that cylinder. A similar stroke adjuster 71 maybe provided at the other end of the actuator cylinder to fix the extentof travel of the mold plate in the fill position. Stroke adjustmentmechanisms 71 are only required on one of the actuator cylinders becausethey are mechanically tied together via their toothed racks and commonpinion.

In prior art machines, the relatively thin sheet metal feed hopper 16 issubject to cyclical forces because of the periodic operation of the feedaugers 30 which are timed generally to coincide with the intermittentoperation of the feed rams 17 with each mold fill cycle. As a result,the walls of the feed hopper actually expand and contract and thiscyclical flexing has resulted in formation of cracks in the bottom ofthe hopper in certain prior art devices. In prior art machines, asindicated above, the cover plate 34 and the entire knock-out device 33supported on the cover plate may be raised vertically to permit accessto the molding station. Attempts have been made in prior art devices toseal the joint between the front wall of the feed hopper 16 and the rearedge of the cover plate which moves vertically with respect to thehopper when raised to access the molding station. Nevertheless, thisjoint is the subject of substantial leakage of food product which addsconsiderably to the difficulty in maintaining a clean operatingenvironment. Referring also to FIG. 11, the improved machine of thepresent invention provides a rigid reinforcing channel member 77 betweenthe front wall of the feed hopper 16 and the rear edge of the coverplate 34 which serves to resolve both of the foregoing problems. Thechannel member 77 has a generally U-shaped cross section with enclosinglateral end walls 78 and a center web 80. The lower edges of the endwalls 78 and the center web 80 are provided with drain openings 81 toassist in cleaning and the removal of any material which may accumulatetherein. Otherwise, the channel member 77, because of its rigidconstruction, provides a rigid support for the lower portion of the feedhopper 16 to which it is securely attached. The rear edge of the coverplate is defined by a vertical rear face 82 which is provided with asuitable groove to receive an O-ring seal 83. When the cover plate is inits operative position, as shown in the drawings, the O-ring sealprevents the escape of liquid and solid material as a result of highmolding pressures imposed on the underlying mold components. When thecover plate is lifted to access the molding station, the seal simplyrides along therewith. The upper edge of the front face of the channelmember 77 is provided with a chamfer 84 to facilitate downward movementof the cover plate and O-ring seal 83 when the cover plate is returnedto its operative position.

I claim:
 1. An apparatus for operating a food product molding machinehaving a feed ram device receiving a food product from a supply andtransferring said food product into a mold cavity of a mold plate in afill position, wherein said mold plate is cycled in a linear reciprocalpath defined by a return stroke to a fill position and an oppositedischarge stroke to a discharge position, a product discharge deviceoperable while the mold plate is held for a discharge dwell time in thedischarge position to remove the product from the mold cavity, and aplate shuttle supporting the mold plate for movement therewith along thelinear mold path, the apparatus comprising:(1) means for driving theplate shuttle to cycle the mold plate in said linear reciprocal path;(2) means responsive to a fill-on control signal for commencing forwardmovement of the feed ram device and the feed of a moldable food productto the mold plate cavity; (3) means responsive to a fill-off controlsignal for terminating forward movement of said feed ram device and thefeed of the food product to the mold cavity; and, (4) means responsiveto a discharge position signal for holding the mold plate for aselectively variable discharge dwell time.
 2. The apparatus as set forthin claim 1 wherein said fill-on signal is generated during the returnstroke.
 3. The apparatus as set forth in claim 1 wherein said fill-offsignal is generated during the discharge stroke.
 4. The apparatus as setforth in claim 1 including means responsive to a fill position signalfor holding the mold plate in the fill position for a selectivelyvariable fill dwell time.
 5. The apparatus as set forth in claim 1wherein said feed ram device comprises a pair of alternately operablefeed rams, and including:means responsive to an end of a ram feed strokesignal for reversing one of said rams and for commencing the feed strokeof the other of said rams; and, delay means for holding a response ofthe other of said rams to said end of ram feed stroke signal untilgeneration of a next fill-off signal.
 6. The apparatus as set forth inclaim 4 including means for adjusting the discharge dwell time inresponse to a change in fill dwell time to maintain a constant moldplate cycle time.